In mobile communication, it is common that a terminal (to be referred to as “user apparatus UE” hereinafter) and a base station eNB perform communication so that communication is performed between user apparatuses UE. However, in recent years, various techniques are considered on D2D communication for performing direct communication between user apparatuses UE (non-patent document 1, for example). When performing communication between user apparatuses UE, a user apparatus UE receives a discovery signal from another neighboring user apparatus UE so as to discover the user apparatus UE which becomes a communication partner of D2D, and to perform D2D communication with the user apparatus UE by performing connection setup and the like with the user apparatus UE.
By the D2D communication, it becomes possible to offload traffic between user apparatus UE-base station eNB, and to perform communication even when communication becomes unavailable in the base station eNB due to disaster and the like.